Investigators are focusing on train warnings

Edward A. Ornelas/San Antonio Express-News

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National Transportation Safety Board member Mark Rosekind (center) speaks during a press conference at the scene of the crash, Friday Nov. 16, 2012, involving a Union Pacific train and a parade float carrying military veterans in Midland, Tx. Four veterans were killed in the accident which occurred Thursday afternoon.

National Transportation Safety Board member Mark Rosekind (center) speaks during a press conference at the scene of the crash, Friday Nov. 16, 2012, involving a Union Pacific train and a parade float carrying military veterans in Midland, Tx. Four veterans were killed in the accident which occurred Thursday afternoon.